CRANIOCERVICAL DECOMPRESSION FOR CHIARI-I MALFORMATION - A RETROSPECTIVE EVALUATION OF FUNCTIONAL OUTCOME WITH PARTICULAR ATTENTION TO THE MOTOR DEFICITS

We report a series of 26 patients affected by a Chiari I malformation treated at our department between 1987 and 1993. All patients underwen t pre- and postoperative evaluation by magnetic resonance imaging (MRI ). Sequential perioperative motor evoked potential (MEP) recordings we re performed in 8 patients. The preoperative symptoms can be divided i nto four subgroups: cephalgias (84.6%), cranial nerve deficits (69.2%) , motor deficits (76.9%), sensory deficits (73%). Twenty-five out of 2 6 patients underwent craniovertebral decompression, 1 a transoral ante rior decompression. One patient died 2 months after surgery because of progressive pulmonary failure. We registered following postoperative complications: transient hypoglossal palsy (1 case), vertigo (2 cases) , meningitis (1 case), minor CSF leaks (3 cases). Cephalgias subsided in 17 and improved in 4 out of 22 patients. Cranial nerve deficits imp roved in 8 and were stabilized in 7 out of 18 patients. A limited reco very of trigeminal function was possibly due to nuclear lesions. Five patients whose vestibular disturbances were not relieved by surgery we re put on a course of carbazepine. Vertigo resolved in one case and in two others improved. While hypesthesia improved after decompression, the other sensory deficits were stabilized in 5% of the patients. Spas ticity improved in 12 out of 18 patients, but weakness only in 7 out o f 17 patients. Motor disturbances were always detected by MEP-recordin g. MEP-characteristics were not specific, resembling those of patients with other intra-, extramedullary myelopathies. Functional recovery w as not matched by an improvement of the MEP parameters. MEP may be use d as a tool for survellance of patients whose clinical findings are no t progressive and are not at first surgical candidates.